In general, it is known to apply a high voltage to food and to put the food in an electrical field atmosphere for preserving freshness of the food or facilitating a maturing processing of the food. Such the electrical field atmosphere is formed by an electric power source having a voltage of from 2 kV to 10 kV and a commercial electric power source frequency (50 or 60 Hz). When conducting a freshness preservation processing or a maturing processing of food, the inside of a refrigerator is kept at a temperature of from 0 to −2° C., and the electrical field atmosphere is formed by the above-mentioned electric power source merely. In addition, it is also known that the electrical field has a function of inhibiting growth of bacterium attached to food and that the electrical field is applied to fermented beverage.